Echorec Multi-Section Electrolytic Capacitor Rebuild
by Phil Taylor
If your Echorec still has an original factory electrolytic power supply capacitor installed than it will almost certainly need replacing. This is because the electrolyte inside the capacitor slowly evaporates away over time just like when the acid level drops in a car battery, however unlike a car battery you can’t top up a capacitor with water. As the electrolyte drys up the capacitor gradually loses capacitance and it’s internal resistance can also become lower degrading its performance. The capacitor needs replacing.
The Echorec utilises a two section capacitor for smoothing in its power supply. In the good old days multi-section capacitors were all the rage where several capacitors would be installed in one can, however they’re now difficult to find, expensive or unobtainable. Not to worry though – there are many people rolling their own multi-section caps. It’s quite easy to do and less expensive than buying a reissue or N.O.S. part and the performance will almost certainly be better too as today’s increasing demand for high power switched-mode power supplies means there is a wide selection of low ESR, high-voltage electrolytic capacitors to choose from.
I chose two stubby little 47μF 350V capacitors as they were the right size to fit inside the aluminium can when stacked on top of each other. The can is easily disassembled by filing around the top lip where it is clinched around the plastic lid. Another method of getting into the can is to saw through the end with a fine jewellers saw. Bending the can is not recommended as it will distort it’s shape.
The plastic lid can be removed. Next a rubber O-ring needs to be pried out. It should then be possible to remove the contents which look like lump of wet cotton wool. This is mess contains the aluminium foil electrodes and dielectric which is quite acidic – the working part of the capacitor. Make sure you wash you hands or wear protective gloves if neccessary. You can now clean up the inside of the can to install the capacitors. The negative pin of each capacitor should be connected together and they will need to be brought out of the top of the can as an earth as the can is no longer connected.